Q. 55 mph to 70 mph truck shakes at low rpm. Want to raise the RPMs s shake goes away. It seems to be fuel related. Sometimes I have to put my foot into it to clear up and get the power it used to have. - Val

A.  I'm going to guess that you have a bad injector.  They will usually shutter and shake under light throttle when the truck is in overdrive at lower rpms.  I would check for trouble codes and see if there are any stored for an injector.